1. Field of the Invention
The present invention relates to an automotive alternator provided with a blowing means.
The entire content of the basic Japanese Patent Application from which the priority under the Convention is claimed in this application is hereby incorporated by reference into this application.
2. Description of the Related Art
FIG. 25 is a cross section of a conventional automotive alternator, and FIGS. 26 and 27 are front elevations showing a front-end fan and a rear-end fan, respectively, used in a rotor of the conventional automotive alternator.
This automotive alternator is constructed by rotatably mounting a Lundell-type rotor 7 by means of a shaft 6 inside a case 3 constructed from an aluminum front bracket 1 and an aluminum rear bracket 2, and fastening a stator 8 to an inner wall of the case 3 so as to cover an outer circumferential side of the rotor 7.
The shaft 6 is rotatably supported in the front bracket 1 and the rear bracket 2. A pulley 4 is fastened to a first end of this shaft 6 such that rotational torque from an engine can be transmitted to the shaft 6 by means of a belt (not shown).
Slip rings 9 for supplying electric current to the rotor 7 are fastened to a second end of the shaft 6, and a pair of brushes 10 are housed in a brush holder 11 disposed inside the case 3 such that the pair of brushes 10 slide in contact with the slip rings 9. A regulator 18 for adjusting the magnitude of alternating voltage generated in the stator 8 is fastened by adhesive to a heat sink 17 fitted onto the brush holder 11. A rectifier 12 which is electrically connected to the stator 8 and converts alternating current generated in the stator 8 into direct current is mounted inside the case 3.
The rotor 7 is composed of a rotor coil 13 for generating magnetic flux on passage of electric current, and a pair of Lundell-type front-end and rear-end pole cores 20 and 21 disposed so as to cover the rotor coil 13, magnetic poles being formed in the front-end and rear-end pole cores 20 and 21 by magnetic flux generated in the rotor coil 13. The pair of front-end and rear-end pole cores 20 and 21 are made of iron, each has a number of front-end and rear-end claw-shaped magnetic poles 22 and 23 disposed on an outer circumferential perimeter at even pitch in a circumferential direction so as to project axially, and the front-end and rear-end pole cores 20 and 21 are fastened to the shaft 6 facing each other such that the front-end and rear-end claw-shaped magnetic poles 22 and 23 intermesh.
The front-end and rear-end fans 5A and 5B are each prepared by form-working a metal plate, and each includes an annular fan base portion 5a, a number of blade base plates 5b extending radially outwards from outer peripheral portions of the fan base portions 5a, and blades 5c formed by folding and bending an outer peripheral portion of each of the blade base plates 5b. The front-end and rear-end fans 5A and 5B are fastened to front and rear axial ends of the front-end and rear-end pole cores 20 and 21, respectively.
The stator 8 is constituted by a stator core 15, and a stator coil 16 formed by winding a conducting wire into this stator core 15, alternating current being generated in the stator coil 16 by changes in magnetic flux from the rotor 7 accompanying rotation of the rotor 7. Portions of the stator coil 16 extend from front and rear axial ends of the stator core 15 and constitute a front-end coil end group 16f and a rear-end coil end group 16r. 
In automotive alternators constructed in this manner, electric current is supplied from a battery (not shown) through the brushes 10 and the slip rings 9 to the rotor coil 13, generating magnetic flux. The front-end claw-shaped magnetic poles 22 in the front-end pole core 20 are magnetized with north-seeking (N) poles by this magnetic flux, and the rear-end claw-shaped magnetic poles 23 in the rear-end pole core 21 are magnetized with south-seeking (S) poles. At the same time, rotational torque from the engine is transmitted through the belt and the pulley 4 to the shaft 6, rotating the rotor 7. Thus, a rotating magnetic field is applied to the stator coil 16, generating electromotive force in the stator coil 16. This alternating electromotive force passes through the rectifier 12 and is rectified into direct current, the output thereof is adjusted by the regulator 18, and the battery is recharged.
In this automotive alternator, the rotor coil 13, the stator coil 16, the rectifier 12, and the regulator 18 continuously generate heat during power generation, and in an alternator having a rated output current in the 100A class, these components generate 60W, 500W, 120W, and 6W of heat energy, respectively, at rotational frequencies at which the temperature is high.
Thus, in order to cool the heat generated by power generation, front-end and rear-end air intake apertures 1a and 2a and front-end and rear-end air discharge apertures 1b and 2b are disposed in the front bracket 1 and the rear bracket 2. More specifically, as shown in FIG. 25, a number of the front-end and rear-end air intake apertures 1a and 2a are disposed in lines circumferentially in axial surfaces (end surfaces) of the front bracket 1 and the rear bracket 2, respectively, and a number of the front-end and rear-end air discharge apertures 1b and 2b are disposed in lines circumferentially in radial surfaces (side surfaces) of the front bracket 1 and the rear bracket 2, respectively.
At the rear end, as indicated by arrows in FIG. 25, external air is sucked into the case 3 through the rear-end air intake apertures 2a by rotation of the rear-end fans 5B, cooling the rectifier 12 and the regulator 18, and is then deflected centrifugally by the rear-end fans 5B, cooling the rear-end coil end group 16r of the stator coil 16 before being expelled to the outside through the rear-end air discharge apertures 2b. At the same time, at the front end, as indicated by arrows in FIG. 25, external air is sucked into the case 3 through the front-end air intake apertures 1a by rotation of the front-end fans 5A and is then deflected centrifugally by the front-end fans 5A, cooling the front-end coil end group 16f of the stator coil 16 before being expelled to the outside through the front-end air discharge apertures 1b. In addition, a cooling air flow flows from the front end to the rear end as a result of a pressure difference between the front end and the rear end, cooling the rotor coil 13.
When the conventional automotive alternator constructed in this manner is operated at a rotational frequency of 5000 rpm, the air flow rate in each of the ventilation pathways has been such that the front-end intake air flow rate QfIN was 0.025 m3/s, the front-end discharge air flow rate QfOUT was 0.02 m3/s, the rear-end intake air flow rate QrIN was 0.03 m3/s, the rear-end discharge air flow rate QrOUT was 0.035 m3/s, and the front-to-rear air flow rate Qfxe2x86x92r was 0.005 m3/s.
This conventional automotive alternator is constructed such that the rear-end flow rates are greater than the front-end flow rates. Thus, at the rear end, because the large volume of cooling air taken in through the rear-end air intake apertures 2a is warmed as it cools the rectifier 12 and the regulator 18 and is then supplied for the cooling of the rear-end coil end group 16r of the stator coil 16, temperature increases in the rear-end coil end group 16r cannot be sufficiently suppressed. Similarly, at the front end, because the small volume of cooling air taken in through the front-end air intake apertures 1a is supplied for the cooling of the front-end coil end group 16f of the stator coil 16, temperature increases in the front-end coil end group 16f cannot be sufficiently suppressed. In other words, one problem has been that overall cooling efficiency has been low because the front-end flow rates have been too low to effectively cool the stator coil 16.
Now, fan-generated noise (SPL: Sound Pressure Level) is expressed by SPL=k+10 log(P2.5xc3x97Q), and is significantly affected by pressure loss P and by flow rate Q at the work point. Moreover, k is the specific sound level, being the noise per unit pressure and flow rate.
The relationship between pressure loss (P), flow rate (Q), and wind resistance (r) is generally expressed by P=rxc3x97Q2.
Thus, in the case of an identical flow rate, pressure loss becomes increasingly excessive as wind resistance increases, causing SPL to worsen significantly.
Consequently, another problem in conventional automotive alternators has been that noise is increased because the flow rates in the rear end where the wind resistance is higher are greater than in the front end, as mentioned above.
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator enabling overall cooling efficiency to be raised by making front-end flow rates capable of effectively cooling coil ends of a stator coil greater than rear-end flow rates so that the stator coil can be cooled sufficiently, and increasing the capacity of a rear-end blowing means relative to the capacity of a front-end blowing means to ensure rear-end flow rates so that a rectifier and a regulator are sufficiently cooled, and in addition, enabling noise to be reduced by making the flow rates in the front end, where wind resistance is small, greater than the flow rates in the rear end, where wind resistance is great.
In order to achieve the above object, according to one aspect of the present invention, there is provided an automotive alternator including:
a rotor fastened to a shaft rotatably supported by a front bracket and a rear bracket, the rotor having a pair of Lundell-type pole cores disposed inside the brackets;
a stator supported by the brackets, the stator being disposed so as to cover an outer circumference of the rotor, the stator comprising:
a cylindrical stator core in which a plurality of slots having grooves lying in an axial direction are disposed circumferentially so as to open onto an inner circumferential side; and
a stator coil installed in the stator core so as to constitute a predetermined winding construction;
a pulley fastened to a front end of the shaft; and
a rectifier disposed at a rear end of the rotor,
wherein
a plurality of front-end and rear-end air intake apertures are disposed in axial end surfaces of the front and rear brackets, respectively;
a plurality of front-end and rear-end air discharge apertures are disposed in radial side surfaces of the front and rear brackets, respectively; and
front-end and rear-end blowing means are disposed at front and rear axial ends of the rotor, respectively,
whereby a front-end ventilation pathway in which a cooling air flow flows through the front-end air intake apertures into the front-end bracket and flows out through the front-end air discharge apertures, a rear-end ventilation pathway in which a cooling air flow flows through the rear-end air intake apertures into the rear-end bracket and flows out through the rear-end air discharge apertures, and a front-to-rear ventilation pathway in which a cooling air flow flows through an inner side of the rotor between the front end and the rear end each is generated by operation of the blowing means,
wherein a capacity of the rear-end blowing means is greater than a capacity of the front-end blowing means, and a front-end air intake flow rate is greater than a rear-end air intake flow rate.
A front-end air discharge flow rate may be greater than a rear-end air discharge flow rate.
According to another aspect of the present invention, there is provided an automotive alternator including:
a rotor fastened to a shaft rotatably supported by a front bracket and a rear bracket, the rotor having a pair of Lundell-type pole cores disposed inside the brackets;
a stator supported by the brackets, the stator being disposed so as to cover an outer circumference of the rotor, the stator comprising:
a cylindrical stator core in which a plurality of slots having grooves lying in an axial direction are disposed circumferentially so as to open onto an inner circumferential side; and
a stator coil installed in the stator core so as to constitute a predetermined winding construction;
a pulley fastened to a front end of the shaft; and
a rectifier disposed at a rear end of the rotor,
wherein
a plurality of front-end and rear-end air intake apertures are disposed in axial end surfaces of the front and rear brackets, respectively;
a plurality of front-end and rear-end air discharge apertures are disposed in radial side surfaces of the front and rear brackets, respectively; and
front-end and rear-end blowing means are disposed at front and rear axial ends of the rotor, respectively,
whereby a front-end ventilation pathway in which a cooling air flow flows through the front-end air intake apertures into the front-end bracket and flows out through the front-end air discharge apertures, a rear-end ventilation pathway in which a cooling air flow flows through the rear-end air intake apertures into the rear-end bracket and flows out through the rear-end air discharge apertures, and a front-to-rear ventilation pathway in which a cooling air flow flows through an inner side of the rotor between the front end and the rear end each is generated by operation of the blowing means,
wherein a capacity of the rear-end blowing means is greater than a capacity of the front-end blowing means, and a front-end air discharge flow rate is greater than a rear-end air discharge flow rate.
The front-to-rear ventilation pathway may be blocked.
The front-end and rear-end blowing means may be the Lundell-type pole cores or fans.
The front-end blowing means may be one of the Lundell-type pole cores and the rear-end blowing means may be a fan.
The front-end and rear-end blowing means may be fans, each fan comprising:
a generally annular fan base portion;
a plurality of blade base plates extending radially outwards from outer circumferential edge portions of the fan base portion; and
a plurality of blades standing on an outer circumferential edge portion of each of the plurality of blade base plates.
The rear-end fan may be provided with a greater number of blades than the front-end fan.
A maximum blade height of the rear-end fan may be greater than a maximum blade height of the front-end fan.
The blade base plates of the rear-end fan may be formed into a shape which blocks valley portions between adjacent magnetic poles of the rotor.
A shielding plate may be disposed for blocking air gaps formed by the blade base plates of the rear-end fan and valley portions between adjacent magnetic poles of the rotor.
The stator coil may be constructed by:
inserting coil segments composed of short conductors formed into a general U shape from a first end of the stator core into slot pairs in which the slots in each pair are a predetermined number of slots apart; and
circumferentially bending and joining together free end portions of the coil segments extending outwards at a second end of the stator core from slots the predetermined number of slots apart so as to constitute the predetermined winding construction,
wherein turn-end coil ends formed by U-shaped turn ends of the coil segments are aligned in rows circumferentially to constitute a turn-end coil end group, and joint-end coil ends formed by the joining of the free end portions of the coil segments are aligned in rows circumferentially to constitute a joint-end coil end group.
The joint-end coil end group of the stator coil may be disposed at the front end of the stator core.
The stator coil may be constructed by linking a plurality of winding sub-portions so as to constitute the predetermined winding construction,
wherein each of the winding sub-portions is constituted by one strand of wire constituted by a large number of straight portions housed inside the slots and a large number of turn portions linking together end portions adjacent straight portions outside the slots, the strand of wire being installed in the stator core by housing the straight portions so as to form different layers relative to a slot depth direction in slots the predetermined number of slots apart, and coil ends formed by the turn portions are aligned in rows circumferentially to constitute front-end and rear-end coil end groups of the stator coil.